Detailed and accurate timing delay analysis is a critical step in the successful design of modern complex integrated circuits. In order to determine whether a proposed circuit implementation will meet key design criteria including at-speed operation, timing delay analysis of the proposed circuitry must be performed as accurately and efficiently as possible at numerous stages of the design process. Results of the detailed analysis of circuit delay directly impact logic synthesis, circuit placement, routing of interconnect, and the like. Further, optimization that may be performed late in the design cycle has a direct impact on system performance. Although detailed transistor-level circuit simulation could in theory be performed, such analysis is not remotely practical primarily because rigorous analysis of the proposed circuit results in immense computational requirements, test overhead, cost, and the like. Techniques such as static timing analysis have been used that provide analysis time speed-up but with limited simulation accuracy because such tests are based on simplified delay models. Ever-increasing complexity and density of modern complex integrated circuits demand improvements in analysis time efficiency of the circuit timing analysis.
Timing delay analysis accuracy and computational efficiency are conflicting but critical design objectives. Computational inefficiencies arise due to increased circuit complexity, accuracy limitations of the delay calculations, overly simplified delay models, lack of specific test cases, simplified signal waveforms, underestimation of wiring complexities, overestimation of worst case delay, and so on. Delay models are typically based on the assumption of input signal independence. Integrated circuit operation however is strongly dependent on critical path analysis, corner analysis, input signal behavior, and the like. In addition, many of the common challenges of chip design can be traced to interface timing problems between different components of the system design. In order to support practical circuit design, various timing estimation techniques have been proposed that provide some simulation time improvements over detailed circuit analysis. Various timing considerations must be made including setup time, hold time, propagation delays, and the like. Timing variations can be due to many design factors, process corners, varying input data, previous operations of the circuit, temperature, voltage, process variations, and the like.